I still do not see why after-init-hook is not called. This question refers to the command-line processing part of after-init-hook, so I tried different configurations, terminals and (non-)window modes.

Why after-init-hook is not called?

Does this mean, other packages with init hooks can also fail?

Edit: Using emacs 26.2, Manjaro Linux 18.0.4 xfce

Update: after rewriting my theme and addressing an issue in spacemacs-theme, after-init seems to work so far via heaven-and-hell. emacs-startup hook had other issues like additional syntax highlighting via prog-mode-hook did not work.

Update 2: The example test.el perhaps always fails. If you run without -Q it is invoked: emacs -l test.el:

ok, I just guessed loading el-files must come earlier than after-init-hook processing (5. It does some basic parsing of the command-line arguments.?). Otherwise is there a way at all for loading custom init files via command line besides of the hardcoded options?
– tddJul 12 at 7:18

I can answer my comment: No. See here: after-init-hook: This normal hook is run, once, just after loading all the init files (site-start.el, your init file, and default.el), before loading the terminal-specific library (if started on a text terminal) and processing the command-line action arguments.
– tddJul 12 at 7:30